Subjects: Dynamic and Electric Engineering >> Engineering Thermophysics submitted time 2024-03-26
Abstract： In this short letter, we report an experimental investigation on the integration of film cooling for thermal protection in a 72-mm cylindrical rotating detonation engine (RDE). The cooling scheme involves injection of cooling air through a series of cat-ear-shaped film cooling holes densely distributed along the outer wall of the cylindrical combustor. Our findings reveal the successful initiation of the RDE and sustained propagation of the rotating detonation wave (RDW) when film cooling is activated and the outflow reaches a supersonic state. Experimental observations corroborate the numerical simulations, indicating a lateral expansion tendency of the cooling jet under the influence of the high-frequency RDW.
Subjects: Dynamic and Electric Engineering >> Electrical Engineering submitted time 2024-03-07
Abstract： The large-scale integration of renewable energy into the power grid leads to the decrease of short circuit ratio (SCR) and system voltage support strength, which results in stability issues such as static voltage stability problems and sub/super synchronous oscillation. Grid-forming (GFM) converters have effective voltage support capacity and equipping renewable energy stations with a certain proportion of GFM converters can improve the stability of the system. However, the analytical relationship between the capacity of GFM converters and the stability margin is unclear, which is difficult to estimate the required proportions of GFM converters theoretically. Therefore, from the perspective of small signal stability, this paper discusses the estimation method and typical values of the capacity ratios between GFM converters and grid-following (GFL) converters. Firstly, based on the voltage-source equivalent analysis of GFM converters, the influence of the capacity ratios on the system strength and stability margin is analyzed through the generalized short circuit ratio (gSCR) index. Secondly, considering changing some of the wind turbines into GFM control and installing new GFM converters, the typical values of the capacity ratios in practical engineering are discussed based on typical parameters of step-up transformers and using relevant industry standards as boundary conditions. The validity of the conclusion is verified by simulation results of the multi-wind-farm system.
Subjects: Dynamic and Electric Engineering >> Other Disciplines of Dynamic and Electric Engineering submitted time 2024-02-07 Cooperative journals: 《应用力学学报》
Abstract：
The vibro-impact process is simplified by the instantaneous impact model,but the classical Newton’s restitution coefficient model adopted brings errors in the calculation.In this paper,a modified restitution coefficient model is introduced to replace the classical Newton’s model of restitution coefficient,and the stochastic response of a class of vibro-impact systems with bilateral barriers under broad-band noise excitation is investigated.Based on the energy levels of the system,its motion can be categorized into two types:non-colliding vibration and bilateral collision vibration.Subsequently,the average drift and diffusion coefficients for these two types of motion are determined using the energy envelope random averaging method.On this basis,the corresponding Fokker-Planck-Kolmogorov(FPK)equation is established and solved,leading to the steady-state response of the system.For illustration,the proposed method is applied to the Duffing oscillator.The effects of the yield velocity,interval and the noise excitations on the PDFs of stationary responses are examined,and the validation of analytical results is verified by the Monte Carlo simulation data.
Subjects: Dynamic and Electric Engineering >> Other Disciplines of Dynamic and Electric Engineering submitted time 2024-02-07 Cooperative journals: 《应用力学学报》
Abstract：
The marine towed system is a typical rigid-flexible multi-body system.It should be pointed out that up to now,the damping effect on dynamics of marine towed cable system has not been fully considered in most of the studies.However,in the structural dynamic analysis of marine towed system,especially in the dynamic response analysis of towed cable rotation process,the damping effect cannot be ignored.The modal characteristics of the cables are also highly complex due to damping.In order to study the influence of Rayleigh damping on the rotation process of towed cable,with the basis of the lumped mass method,the expression form of Rayleigh damping in towed cable system is further sorted and decomposed,and the influence of each damping component is summarized.Some general conclusions are obtained,which have certain guiding significance for actual towing operation at sea.
Subjects: Dynamic and Electric Engineering >> Other Disciplines of Dynamic and Electric Engineering submitted time 2024-02-07 Cooperative journals: 《应用力学学报》
Abstract： The on-orbit deployment of the spatial structure involves the complex high-dimensional nonlinear dynamic problems,the analysis on which is one of the challenges in the astrodynamics field and the precondition of performing the control strategy on the on-orbit deployment process.In this paper,taking the 1st deploying stage of the IKAROS solar sail as an example,the flexible stretching hub-beam model is proposed and the dynamic equation for which is presented based on the Hamiltonian variational principle.Employing the complex structure-preserving method which focuses on the local dynamic behaviors of the system,the 1st deploying process of the IKAROS solar sail is simulated under two working conditions(invariable torque and constant power)respectively.The numerical results show that the differences between the rotational velocities of the hub for the two cases are remarkable.The rotational stability of the hub turns bad with the invariable torque,which results in the large work needed in the 1st deploying stage of the IKAROS solar sail and implies that the constant power working condition can save energy in this process.
Subjects: Dynamic and Electric Engineering >> Other Disciplines of Dynamic and Electric Engineering submitted time 2024-02-07 Cooperative journals: 《应用力学学报》
Abstract：
This paper introduces a cable damage identification method for cable-stayed bridges based on principal component analysis(PCA)to facilitate efficient cable damage detection.The proposed approach involves collecting the acceleration response of the cable structure when subjected to a moving load.Subsequently,the PCA method is employed to reduce the dimensionality of the time-domain signal.Statistical data are then extracted from the reduced dimension signal,and a multi-order statistical moment fusion index is constructed using the Dempster-Shafer(D-S)evidence theory for identification purposes.Using the Yonghe Bridge in Tianjin as a case study,the paper explores the impact of cable damage degree,load mass,and load moving speed on damage identification accuracy through finite element numerical simulations.The analysis results demonstrate the efficacy of the proposed method,highlighting its robust recognition capabilities and resilience to noise.The developed approach proves to be a promising tool for accurate and timely identification of cable damage in cable-stayed bridges,contributing to enhanced structural safety and maintenance practices.
Subjects: Electronics and Communication Technology >> Electron Technology Subjects: Dynamic and Electric Engineering >> Electrical Engineering submitted time 2024-01-30
Abstract： In the scope of our investigation, we have solved the stability problem of the boost converter. Ouyang Changlian's doctoral dissertation made me realize the importance of duty cycle in control system.
Peer Review Status:
Awaiting Review
Subjects: Dynamic and Electric Engineering >> Engineering Thermophysics submitted time 2024-01-06
Abstract： With the continuous progress of industrial technology, deep learning, as an important branch of artificial intelligence, has brought new possibilities to various fields. In this paper, the optimal location of diesel engine vibration monitoring is studied, focusing on the problem of data overlap and mutual interference in vibration monitoring. By discussing the best position and number of sensors on diesel engine, a method of sensor layout optimization based on graph pool neural network is proposed. In this method, the sensor points are regarded as the nodes of the graph, and the adjacency matrix is processed by the convolution layer of the graph, and the eigenvector of each node is obtained. The feature vectors are screened and sorted by information entropy and independence methods, and the representative feature vectors are selected as important nodes. Finally, classification and screening are carried out in the pooling layer, taking into account factors such as coverage and cost, so as to determine the optimal sensor placement and number.
The experimental results show that the proposed graph pool network model can effectively optimize the layout of sensor measuring points, and has high accuracy and stability. This method is not only suitable for diesel engine vibration monitoring, but also can be extended to other problems requiring sensor layout optimization.
Peer Review Status:Awaiting Review
Subjects: Dynamic and Electric Engineering >> Engineering Thermophysics submitted time 2024-01-06
Abstract： With the promotion of "Industry 4.0" and "Intelligent Manufacturing 2025", intelligent equipment is becoming the future development direction of high-end equipment. In this process, the fault diagnosis and identification system, as an important research field, can suppress the unbalanced vibration of machinery in real time, so as to realize the autonomous health of equipment. Such a system can not only improve the operational efficiency and productivity of the equipment, but also reduce the cost and risk of equipment maintenance. Therefore, the research and development of such systems is of great significance to promote the development of intelligent manufacturing and high-end equipment manufacturing.
Condition monitoring and fault diagnosis of large rotating machinery is a necessary means for the production management of modern enterprises, through scientific monitoring and diagnosis, the efficient, safe and reliable operation of the equipment can be realized, and the sustainable development of the enterprise can be provided with a strong guarantee. This project takes the typical vibration faults of the rotor system of rotating machinery as the main body of research, considers the analysis of them, and establishes an intelligent identification system for the diagnosis of typical faults of the rotor system of rotating machinery. The main research contents and conclusions of this paper are as follows:
(1) This paper summarizes and explores the current mechanical intelligent fault diagnosis algorithm and the research method of using neural network for fault classification by consulting relevant literature, and finally decides to choose RBF neural network for fault diagnosis and classification.
(2) PCA dimensionality reduction technology is used to reduce the dimension of the data after extracting features, so as to reduce the dimension of the data to solve the problem of "dimensionality disaster" and make the data more reliable;
(3) The fault classification software is established by using the radial basis neural network in the artificial neural network, and the fault is identified by the classifier and verified by relevant experiments to complete the classification software design;
(4) A test bench was set up to collect data for relevant experimental verification, and the experiment showed that the diagnostic accuracy reached more than 85%.
Peer Review Status:Awaiting Review
Subjects: Dynamic and Electric Engineering >> Engineering Thermophysics submitted time 2024-01-05
Abstract： Many key equipment rely heavily on the high-powered medium to high speed diesel engine, which has a broad range of applications in areas such as ships and nuclear power. Due to the complex mechanical structure and ever-changing working environment, diesel engine equipment accidents occur frequently, and mechanical failures and equipment damage are becoming increasingly prominent. Frequent failures have become a major challenge for the operation of these equipment. The occurrence of malignant faults in diesel engines often leads to serious economic losses and casualties. Therefore, using reasonable methods to obtain fault characteristics, researching fault detection and early diagnosis methods for diesel engines, achieving early warning and timely diagnosis of diesel engine faults, plays an important role and value in improving the stability of high-power, medium and high-speed diesel engine operation, equipment safety, and enterprise economy.
This article extracts 22 vibration characteristics of diesel engines in the angular domain, time domain, and frequency domain to form a feature set. In response to the diverse and complex operating conditions of diesel engines, with only a small number of operating samples, this article uses neural networks to map the relationship between operating conditions and key parameters in the Markov space, and constructs a healthy baseline for diesel engines under variable operating conditions.
Peer Review Status:Awaiting Review
Subjects: Dynamic and Electric Engineering >> Electrical Engineering submitted time 2023-12-20
Abstract： With the large-scale integration of renewable energy and power electronic devices, system voltage support strength decreases, thus threatening the system's safe and stable operation. In the homogeneous scenario where power electronic devices integrated into the system have the same dynamics, a theoretically rigorous and highly stable quantitative method for quantifying system voltage support strength can be formed based on the generalized short-circuit ratio(gSCR) and the device critical short-circuit ratio(SCR0) In the heterogeneous scenario where power electronic devices integrated into the system have weakly different dynamics, system voltage support strength can be quantified by the first-order approximation of gSCR and SCR0, based on some special dynamic characteristics of devices and power grid. However, there is a lack of unified calculation principles at the theoretical level. To this end, this paper focuses on quantifying system voltage support strength under small-signal stability and discovers that the multi-infeed system can be approximately decoupled into multiple low-dimensional systems. On this basis, this paper proposes the concept and approximate calculation method of eigen-subsystems and interprets their physical significance. Based on the concept of eigen-subsystems, the general calculation principle of gSCR and SCR0 were unified, which achieves strength quantification of heterogeneous multi-infeed systems. Additionally, the specific calculation methods for gSCR and SCR0 are provided in typical scenarios, such as grid-following converters under non-rated operating conditions, reverse active power output, and considering grid-forming devices. Finally, the effectiveness of the calculation principles and methods is verified in several cases.
Peer Review Status:Awaiting Review
Subjects: Dynamic and Electric Engineering >> Electrical Engineering submitted time 2023-11-29
Abstract： With the development of renewable energy, the voltage support strength of renewable energy multi-infeed systems is gradually decreasing, and there is an urgent need for strength evaluation methods. If considering that converters are all at the rated operating conditions, accurate quantification of strength can be achieved by utilizing existing power grid strength indices and threshold; However, the actual operating conditions are diverse and complex, which disrupts the existing criteria for defining indices and leads to the failure of existing methods. Therefore, this paper focuses on the quantification of voltage support strength under actual operating conditions. Firstly, the mapping relationship between the dynamic characteristics of grid-following converters, operating conditions, and parameters is discovered. Secondly, based on the perturbation theory of characteristics subspaces, an equivalent single-infeed system that can approximate the stability of the actual system is solved. On this basis, the operational generalized short circuit ratio(OgSCR) are defined. A rigorous method for quantifying voltage support strength can be formed based on the OgSCR and the device critical operational short-circuit ratio (OSCR0). In addition, this paper reveals the effect of actual operating conditions on strength. Finally, a numerical example is used to verify the feasibility of the proposed method
Peer Review Status:Awaiting Review
Subjects: Dynamic and Electric Engineering >> Power Machinery Engineering submitted time 2023-10-24
Abstract： Aiming at the problem that the stepless capacity control system of reciprocating compressor has a high failure rate and great impact on the operation of the unit, and the existing risk assessment methods of the compressor operation are difficult to complete the real-time and quantitative risk assessment, a risk dynamic analysis method of the safety of stepless capacity control system was proposed, which integrated Bayes network and variable weight AHP. The Bayesian network model, which included fault type, fault mode and monitoring signal, was established to obtain the real-time probability of fault occurrence. Based on variable weight analytic hierarchy process (AHP), a semi-quantitative analysis model of fault hazard was established, and the influence index of fault mode was calculated. Further, the fault risk calculation formula of FMEA method was modified, the probability of fault occurrence was introduced, and the calculation method of historical fault and real-time operation risk was proposed. The results showed that the new method proposed in this paper could quantify the real-time and historical operating risks of computer units, and the normalized real-time operating risk threshold was setted as 0.5 to determine the need for maintenance. The research results can provide quantitative indexes for the establishment of inspection and maintenance plans for reciprocating compressors and gas volume regulation systems.
Peer Review Status:Awaiting Review
Subjects: Dynamic and Electric Engineering >> Electrical Engineering submitted time 2023-07-28
Abstract： The high penetration of the renewable energy generation brings significant volatility and uncertainty for the power system operation. To address this issue, it is necessary to involve a significant amount of flexible resources for grid dispatch and ancillary services. The numerous, widely distributed, and diverse characteristics of these flexibility resources make cluster-based management difficult, requiring a quantitative evaluation of their power flexibility range. This article proposes a quantification metrics system for aggregating flexible resources based on their application requirements in grid dispatch and the power market. By classifying the energy resources in the cluster into generator-type and storage-type, they are respectively aggregated into equivalent generator and equivalent storage devices as the reference model. The parameters of these two equivalent devices serve as the quantification metrics, possessing intuitive physical meanings, robust nested characteristics, and applicability across multiple time scales. These metrics can be widely applied in many scenarios, such as the asynchronous dispatch of distributed resource clusters, the coordinated optimization dispatch of integrated energy systems, and bidding of virtual power plants participating in the power market.
Peer Review Status:Awaiting Review
Subjects: Dynamic and Electric Engineering >> Electrical Engineering submitted time 2023-06-06
Abstract： System strength is generally used to describe the voltage response performance under a disturbance and quantify the stability margin. The system strength indicated by short-circuit ratio (SCR) has provided a simple and intuitive reference for grid operators. However, the existing SCR-based methods rely on the premise that synchronous generators provide short-circuit capacity and voltage support. Due to this premise, these methods are unsuitable for renewables delivery systems with voltage source converter-based high voltage direct current (VSC-HVDC), where all apparatuses are power-electronic interfaces. This paper aims to respond the system strength evaluation problem in terms of small-disturbance analysis. Firstly, the sensitivity transfer function matrix of the bus voltage to the renewables multi-feed current is derived and the relationship between the voltage performance and stability is illustrated; Secondly, the generalized short-circuit ratio is extended into the renewables VSC-HVDC delivery system based on the voltage-source equivalent modeling of VSC-HVDC; Then, by combing the apparatus critical SCR and generalized short-circuit ratio, a source-grid separation method can be further proposed to quantify the system strength of such a system. The proposed method can assess the static voltage stability margin or small-disturbance synchronous stability margin at the operating point and determine the critical bus of system strength and the optimization path of system strength improvement. Finally, the proposed method is verified by simulation in multiple wind plants with VSC-HVDC.
Peer Review Status:Awaiting Review
Subjects: Dynamic and Electric Engineering >> Electrical Engineering submitted time 2023-04-25
Abstract： There are many impedance-based methods to analyze the oscillation of grid-connected converter system (GCS) via dq frame, sequence frame and polar frame, which can be transformed into each other and are equivalent in judging the stability of the system. However, the discrepancy and adaptation of these methods has not been discussed theoretically. Therefore, the impedance models of GCS are established in above three kinds of coordinates respectively, then the mathematical and physical characteristics of them are analyzed. Secondly, the decoupling of impedance models in different frames are analyzed, and the differences of the impedance criteria in stability analysis and mechanism interpretation are given. Furthermore, the sub-synchronous oscillation caused by the phase-locked loop considering converter four quadrant operation scenario are illustrated, and the existence of open-loop transfer function right half plane poles and its sensitivity to uncertain parameters are analyzed from the nominal performance and robustness of the impedance criteria. On this basis, the adaptation of several impedance criteria of GCS are analyzed. Theoretical analysis and simulations confirm the validity of the proposed conclusion.
Subjects: Dynamic and Electric Engineering >> Electrical Engineering submitted time 2022-12-08
Abstract：多个外特性类似的直流和新能源等电力电子设备/场群同时馈入交流电网后形成了多电力电子馈入系统（简称多馈入系统），是新型电力系统中很典型的一种形态。系统电压支撑强度（简称系统强度）常用于描述该多馈入系统受到扰动后考虑了设备动态的电压响应性能，而电网强度则是描述不考虑设备动态的开环交流电网性能的术语。现有研究一般认为电网强度与系统强度之间存在正相关性，却并未揭示电网强度与系统强度之间的内在联系。为此，本文聚焦于电网受到小扰动后的系统强度问题，从抗扰性、小扰动稳定性以及静态电压稳定性三个角度分析了基于广义短路比的电网强度指标与系统强度指标之间的解析关系。研究表明，广义短路比本质是一种多端口网络的电压电流和电压无功最大灵敏度，是描述多个设备并网点与交流电网等效中心之间的一种综合电气距离指标，它与设备耐受电网的临界短路比之差反映了系统的稳定裕度和抗扰裕度，从而可用于量化系统强度。为了便于应用与实际操作，给出了广义短路比判据的若干个充分条件，并提出了多种从母线视角下量化电网强度的节点广义短路比指标，同时证明了传统CIGRE多馈入短路比本质是一种特殊的节点广义短路比，其保守性较强且场景扩展性较差。最后，对短路比的计算方法和适用场景等进行了探讨，并基于算例验证所提指标的有效性。
Peer Review Status:Awaiting Review
Subjects: Dynamic and Electric Engineering >> Other Disciplines of Dynamic and Electric Engineering submitted time 2022-11-17 Cooperative journals: 《Electrical & Electronic Engineering Research》
Abstract： This article is fully combed the related literature, the application of big data in the archive management innovation with a thorough system of literature analysis, and obtained from file data acquisition, data transmission, data storage, data archives utilization, staff training and safety archives construction aspects of the need to create a file management system based on big data applications. And Finally, this article analyzes the archival management innovation practice and its effect based on big data application in China, and draws the corresponding value conclusion.
Subjects: Dynamic and Electric Engineering >> Other Disciplines of Dynamic and Electric Engineering submitted time 2022-11-17 Cooperative journals: 《Electrical & Electronic Engineering Research》
Abstract： In order to improve the quality of photovoltaic power injected into the grid, a high-voltage flexible direct current (Voltage Source Converter-High Voltage Direct Curren, VSC-HVDC) grid-connected scheme based on a micro-synchronous phasor measurement unit (μPMU) coordinated control strategy is proposed. The four-terminal topology of photovoltaic power plants connected to the grid via VSC-HVDC is designed, and two photovoltaic power plants are connected to the grid via VSC-HVDC model using Matlab/Simulink simulation software to simulate when the light intensity is changed, the photovoltaic power plant is out of operation and the grid voltage occurs In the case of sudden changes, the system voltage, power, and AC side frequency can still maintain stable operation, which verifies the feasibility and effectiveness of the transmission scheme, and improves the stability and power quality of the power grid.
Subjects: Dynamic and Electric Engineering >> Other Disciplines of Dynamic and Electric Engineering submitted time 2022-11-17 Cooperative journals: 《Electrical & Electronic Engineering Research》
Abstract：
In order to improve the convergence of multi-objective differential evolution (DEMO) algorithm while ensuring well distribution, a new method of center mutation-based DEMO (CM-DEMO) is proposed. Firstly, the form of mutation is improved, the center of the population in the current generation is taken as a base vector, and then the direction of difference vector is determined according to the fitness value of the three random vectors of individuals, secondly, the strategy of adaptive crossover probability is given, the crossover probability is determined according to the distribution of fitness value in the population. Test of benchmark functions show that CM-DEMO algorithm has faster convergence rate. Finally, CM-DEMO is applied to environmental economic dispatch of power system. Compared with other methods, the simulation results obtained demonstrate the feasibility and effectiveness of the proposed algorithm for solving the problem.
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